There is a Joseph Peter Raaskopff, son of Mattias & Angela Raaskopff, who was baptized on 22 July 1715 in Wittlich, northeast of Trier, in what is today Rheinland-Pfalz. A Peter Rosskopf immigrated to Russia, arriving in the colony of Volmer on 18 July 1766. He is recorded there on the 1767 Census in Household No. 41.
In 1792, Joseph Roskopf and his family moved from Volmer to Preuss.
- Mai, Brent Alan. 1798 Census of the German Colonies along the Volga (Lincoln, NE: American Historical Society of Germans from Russia, 1999): Vm21, Mv2936.
- Parish records of Wittlich (LDS Film No. 560480).
- Pleve, Igor. Einwanderung in das Wolgagebiet, 1764-1767 Band 4 (Göttingen: Göttinger Arbeitskreis, 2008): 292.